By Andrew Gray, John Irish, Steve Holland and Sabine Siebold

VILNIUS Britain, the United States and global allies were due to unveil new security assurances for Ukraine on Wednesday, after a NATO summit the day before said Kyiv would be welcome in the alliance but stopped short of naming a date or exact conditions.

President Volodymyr Zelenskiy denounced the outcome as "absurd", saying Ukraine deserved a clear timetable while it was fighting against a Russian invasion launched in February 2022.

Instead, a declaration by the G7 world's most industrialised countries "will set out how allies will support Ukraine over the coming years to end the war and deter and respond to any future attack", said a British government statement.

In practice, this would come as bilateral agreements with Kyiv on long-term military and financial aid to keep Ukraine's army and economy running. A White House official said the United States would start such talks with Kyiv "soon".

"We expect more non-G7 allies and partners will want to join afterwards and do their own bilateral versions of this," said the official. The G7 is made up of the United States, Germany, Japan, France, Canada, Italy and Britain.

NATO, an alliance built around mutual security guarantees - the concept that an attack on one is an attack on all - has carefully avoided extending any firm military commitments to Ukraine, worried that would risk taking it closer to a full-on war with Russia.

Ukraine is deeply suspicious of any less-binding security "assurances", given that Russia's invasion already trampled the so-called Budapest Memorandum under which international powers committed to keeping the country safe in exchange for Kyiv giving up its Soviet-era nuclear arms.

MORE ARMS

On Wednesday, Zelenskiy was holding bilateral meetings with the United States, Canada, Germany, Britain, Japan and the Netherlands on the sidelines of the second day of the NATO summit in Vilnius to secure more arms for his counteroffensive.

"More weapons for our warriors, more protection of life for the whole of Ukraine! We will bring new important defence tools to Ukraine," he said on Twitter.

The first sitting of a new NATO-Ukraine Council was also due on Wednesday, a new format designed to tighten cooperation between Kyiv and the 31-nation alliance.

NATO was set up in 1949 to defend allies against any attack from the Soviet Union. After the Cold War ended and some in the West hoped to improve ties with Moscow, a similar NATO-Russia Council was set up in 2002.

NATO stopped that engagement after Russia annexed the Black Sea peninsula of Crimea from Kyiv in 2014 and then went on to back separatist rebels fighting government troops in eastern Ukraine.

Russia's full-scale invasion in 2022 brought war back to Europe's doorstep, reviving Cold War-era animosities.

NATO says Ukraine would not be allowed in while at war with Russia, with Washington and Berlin warning against any moves that could put the alliance in a direct conflict with Moscow.

Backers of Ukraine's swift NATO accession in eastern Europe and elsewhere, on the other hand, have bristled at what they saw as a disappointing outcome of the first day of the summit.

Russia, which says NATO's eastward expansion is an existential threat to its own security, swiftly lashed out.

Dmitry Medvedev, the deputy secretary of Russia's powerful Security Council chaired by President Vladimir Putin, said increasing military assistance to Ukraine by NATO was bringing closer a World War Three.

(Reporting by John Irish, Steve Holland, Justyna Pawlak, Sabine Siebold, Andrew Gray, Max Hunder, Writing by Gabriela Baczynska; Editing by Alex Richardson)